The present invention generally relates to train monitoring and control systems such as end-of-train (EOT) systems or the like, and more particularly to a method and apparatus for determining the overall length of a train.
Knowledge of a train's overall length is often required to ensure safe operation and handling of the train. For example, the length of a train is utilized to assess whether the train has cleared a point on the track such as, for example, a siding or a switch. To ensure that the point has been cleared, the crew of the train may move the train past the point a distance equal to the train's length plus a predetermined safety factor. Normally, this method assures that the train has safely cleared the point. However, if the determined train length is significantly in error, one or more cars of the train may extend past the point possibly resulting a collision with another train.
Presently, train length is either measured directly or estimated by moving the train past a fixed point at a known velocity. A measurement is started when the front of the train passes the point and ended when the end of the train passes that point. The length of the train may then be measured by determining the distance of the front of the train from the point or calculated based on the velocity of the train. However, this method of determining the train's length is subject to human error and may prove time consuming when performed each time cars are added or removed from the train.
Known to the art are end-of-train (EOT) systems which provide a variety of functions once performed by crew riding in the caboose of a train. Two types of EOT systems exist: one-way EOT systems and a two-way EOT systems. Both types of EOT systems provide crew riding in the cab of a locomotive with key end-of-train information such as, for example, brake pipe pressure at the rear of the train, end of train motion, EOT battery condition, and marker light status.
Typically, one-way EOT systems comprises a cab unit mounted in the cab of the lead locomotive of the train and an end-of-train (EOT) unit mounted to the last car of the train. The EOT unit includes a transmitter which transmits last car status information monitored by the unit to a receiver in the cab unit. The cab unit then displays this information to the crew. In two-way EOT systems, the receiver and transmitter of the one-way system are replaced with transceivers which both receive and transmit information between the cab unit and the EOT unit. Thus, in addition to providing end-of-train information to the crew, the two-way EOT system allows the crew to command the EOT unit to release brake line pressure at the rear of the train thereby permitting simultaneous application of brakes at the front and rear of the train. This feature greatly improves the train's emergency braking capability. Consequently, in 1992, Congress amended the Federal Railroad Safety Act to require railroads to install two-way EOT systems by Jan. 1, 1998 on trains traveling over 30 miles per hour or operating on heavy grades.
It is therefore desirable to improve the safety and efficiency of railroad operations by providing apparatus for determining the length of a train utilizing a received signal such as a reference signal from a global positioning system or the like, wherein this determination may be automatically updated as cars are added to or removed from the train. It is further desirable that the apparatus be capable of operation in conjunction with existing EOT systems.